feat: implement sub-visibility toggle

Closes #597

lib/mpv/player/platform/player_android.dart

@@ -12,6 +12,9 @@ class PlayerAndroid extends PlayerBase {
   int? _bufferSizeBytes;
   bool _tunnelingEnabled = true;
 
+  /// Stored subtitle track ID when subtitles are hidden via sub-visibility.
+  String? _hiddenSubtitleTrackId;
+
   @override
   MethodChannel get methodChannel => _methodChannel;
 
@@ -193,6 +196,29 @@ class PlayerAndroid extends PlayerBase {
       case 'tunneled-playback':
         _tunnelingEnabled = value != 'no';
         break;
+      case 'sub-visibility':
+        if (value == 'no') {
+          // Store current subtitle track and disable
+          final current = state.track.subtitle;
+          if (current != null && current.id != 'no') {
+            _hiddenSubtitleTrackId = current.id;
+            await selectSubtitleTrack(SubtitleTrack.off);
+          }
+        } else {
+          // Restore previously hidden subtitle track
+          final storedId = _hiddenSubtitleTrackId;
+          if (storedId != null) {
+            _hiddenSubtitleTrackId = null;
+            final track = state.tracks.subtitle.cast<SubtitleTrack?>().firstWhere(
+                  (t) => t?.id == storedId,
+                  orElse: () => null,
+                );
+            if (track != null) {
+              await selectSubtitleTrack(track);
+            }
+          }
+        }
+        break;
       // Other properties are no-ops for ExoPlayer
     }
   }

lib/widgets/video_controls/desktop_video_controls.dart

@@ -96,6 +96,9 @@ class DesktopVideoControls extends StatefulWidget {
   /// Called to toggle ambient lighting (passed to settings sheet)
   final VoidCallback? onToggleAmbientLighting;
 
+  /// Whether subtitles are currently visible (false = hidden via sub-visibility toggle)
+  final bool subtitlesVisible;
+
   /// Whether to show the queue button
   final bool showQueueButton;
 
@@ -151,6 +154,7 @@ class DesktopVideoControls extends StatefulWidget {
     this.liveChannelName,
     this.isAmbientLightingEnabled = false,
     this.onToggleAmbientLighting,
+    this.subtitlesVisible = true,
     this.showQueueButton = false,
     this.onQueueItemSelected,
   });
@@ -697,6 +701,7 @@ class DesktopVideoControlsState extends State<DesktopVideoControls> {
                 onNavigateLeft: navigateFromTrackToVolume,
                 canControl: widget.canControl,
                 isLive: widget.isLive,
+                subtitlesVisible: widget.subtitlesVisible,
                 showQueueButton: widget.showQueueButton,
                 onQueueItemSelected: widget.onQueueItemSelected,
                 shaderService: widget.shaderService,

lib/widgets/video_controls/video_controls.dart

@@ -256,6 +256,8 @@ class _PlexVideoControlsState extends State<PlexVideoControls> with WindowListen
   bool _showPerformanceOverlay = false;
   // Long-press 2x speed state
   bool _isLongPressing = false;
+  // Subtitle visibility toggle state
+  bool _subtitlesVisible = true;
   // Skip marker button focus node (for TV D-pad navigation)
   late final FocusNode _skipMarkerFocusNode;
   double? _rateBeforeLongPress;
@@ -551,8 +553,28 @@ class _PlexVideoControlsState extends State<PlexVideoControls> with WindowListen
     }
   }
 
-  // ignore: no-empty-block - stub for future subtitle toggle implementation
-  void _toggleSubtitles() {}
+  void _toggleSubtitles() {
+    final currentTrack = widget.player.state.track.subtitle;
+    // No-op if no subtitle track is selected
+    if (currentTrack == null || currentTrack.id == 'no') return;
+
+    final newVisible = !_subtitlesVisible;
+    widget.player.setProperty('sub-visibility', newVisible ? 'yes' : 'no');
+    setState(() {
+      _subtitlesVisible = newVisible;
+    });
+  }
+
+  void _onSubtitleTrackChanged(SubtitleTrack track) {
+    // Reset visibility when user explicitly picks a new subtitle track
+    if (track.id != 'no' && !_subtitlesVisible) {
+      widget.player.setProperty('sub-visibility', 'yes');
+      setState(() {
+        _subtitlesVisible = true;
+      });
+    }
+    widget.onSubtitleTrackChanged?.call(track);
+  }
 
   void _toggleShader() {
     final shaderService = widget.shaderService;
@@ -982,7 +1004,8 @@ class _PlexVideoControlsState extends State<PlexVideoControls> with WindowListen
       onToggleFullscreen: _toggleFullscreen,
       onSwitchVersion: _switchMediaVersion,
       onAudioTrackChanged: widget.onAudioTrackChanged,
-      onSubtitleTrackChanged: widget.onSubtitleTrackChanged,
+      onSubtitleTrackChanged: _onSubtitleTrackChanged,
+      subtitlesVisible: _subtitlesVisible,
       onLoadSeekTimes: () async {
         if (mounted) {
           await _loadSeekTimes();
@@ -2009,7 +2032,8 @@ class _PlexVideoControlsState extends State<PlexVideoControls> with WindowListen
         onToggleAlwaysOnTop: Platform.isMacOS ? null : _toggleAlwaysOnTop,
         onSwitchVersion: _switchMediaVersion,
         onAudioTrackChanged: widget.onAudioTrackChanged,
-        onSubtitleTrackChanged: widget.onSubtitleTrackChanged,
+        onSubtitleTrackChanged: _onSubtitleTrackChanged,
+        subtitlesVisible: _subtitlesVisible,
         onLoadSeekTimes: () async {
           if (mounted) {
             await _loadSeekTimes();

lib/widgets/video_controls/widgets/track_chapter_controls.dart

@@ -73,6 +73,9 @@ class TrackChapterControls extends StatelessWidget {
   /// Whether this is a live TV stream (hides speed settings).
   final bool isLive;
 
+  /// Whether subtitles are currently visible (false = hidden via sub-visibility toggle)
+  final bool subtitlesVisible;
+
   /// Whether to show the queue button
   final bool showQueueButton;
 
@@ -110,6 +113,7 @@ class TrackChapterControls extends StatelessWidget {
     this.onNavigateLeft,
     this.canControl = true,
     this.isLive = false,
+    this.subtitlesVisible = true,
     this.showQueueButton = false,
     this.onQueueItemSelected,
     this.shaderService,
@@ -267,10 +271,12 @@ class TrackChapterControls extends StatelessWidget {
         // Subtitles button
         if (_hasSubtitles(tracks)) {
           final currentIndex = buttonIndex;
+          final hasActiveSubtitle = tracks?.track.subtitle != null && tracks!.track.subtitle!.id != 'no';
+          final isHidden = hasActiveSubtitle && !subtitlesVisible;
           buttons.add(
             _buildTrackButton(
               buttonIndex: currentIndex,
-              icon: Symbols.subtitles_rounded,
+              icon: isHidden ? Symbols.subtitles_off_rounded : Symbols.subtitles_rounded,
               tooltip: t.videoControls.subtitlesButton,
               semanticLabel: t.videoControls.subtitlesButton,
               tracks: tracks,